Conventional detergent bars based on soap for personal washing contains over about 70% by weight total fatty matter (TFM), the remainder being water (about 10-20%) and other ingredients e.g. colour, perfume, preservatives etc. Many particulate materials may also be present which replace some of the soap in the bar while retaining satisfactory processability.
Yield stress needed to cause a flow in a material is of fundamental importance in determining the structural stability and integrity of multiphase composites such as soaps and detergents. Yield stress plays a major role in the processability of soaps and detergents especially in soap processing equipment such as roll mills, plodders, stampers etc.
Milled bars typically have a water content of between 8-15% while `hard` (non-milled) soap bars have water content in the region of 20-35%. Increase in the water content can replace the TFM making it more economical but will tend to soften the soap bar.
GB 2,230,022 discloses the use of polyacrylate and citrate as barrier materials to improve the softening of the washed fabric by clay in detergent powder formulations. U.S. Pat. No. 5,279,756 discloses the use of acrylic polymers and carboxylic acids as sequestering agents in dish washing compositions. ER 8905598 discloses the use of two specific polymers namely acrylic polymer CO-1 (Acrysol LMW-400N), Rohm and Haas, and Acrysol ASE-75 of Rohm and Haas with a molecular weight of 40,000 to make the bar harder, improve foaming and skin feel. It further specifies that `high molecular weight acrylic polymers are used because the higher viscosity of the liquid will make more distinct striations and, since the acrylic polymer is on the surface, provides better lubricity to hands during washing with the detergent bar`. The compositions disclosed in this patent are of fairly low water concentrations where hardening is not a problem.
The present invention differs from the prior art in that it addresses the problem of producing bars with high water content which normally would be soft and pose acute problems in processing and unsatisfactory end use.
It is the basic objective of the present invention to provide for washing compositions with higher water content but retaining the appropriate structural properties and processability. The composition would also have enhanced physical properties such as higher yield stress, lathering, better feel, lower sog/mush and satisfactory cleaning.